Safety device for drills



H. V. JOHNSON. SAFETY DEVICE FOR DRILLS.

APPLICATION FILED APR.12, I920.

Patented May 10,1921.

PTENT OFFICE.

HENRY V. JGL-INSON, OF ST. PATTI], IJZINNESOTA.

SAFETY nnvrcn non prams Specification of Letters Patent.

Patented May 10, 1921.

Application filed April 12, 1920. Serial no. 373,317.

To all whom it'ma z concern:

Be it known that I, Hmvnr V. JonNsoN, a citizen of the United Statesresiding at 7 85 Geranium St. east, St. l aul, in the county of Ramseyand State of Minnesota, have invented certain new and'usefulTmprovements in Safety Devices for Drills; and I do declarethe'following to be a full, clear, and exact description of theinvention such as will enable others skilled in the art to which itappertains to make and use the same.

This invention relates to an improved safety device for use inconnection with a large drill or other tool or machine which is slidablymounted upon a track for vertical sliding movement and one object of theinvention is to provide a safety device which will be held inoperativeunder normal conditions, but which will be released in case thesupporting chain or cable should break and thus permit the safety deviceto engage a rack carried by the track and thus prevent the drill fromsliding downwardly of its own weight. It often happens that thesupporting chain or cable of a large drill of this type will break andthus permit the drill to drop and not only cause damage to thedrill orwork positioned beneath it but also endangers the lives of workmenhandling the drill.

Another object of the invention is to so construct this safetyattachment that it may be associated with a drill of a conventionalconstruction and thus permit it to be used in connection with drillsalready in use.

Another object of the invention is to so construct this safetyattachment that it will be of very simple construction and very easy toapply.

This invention is illustrated in the accompanying drawing wherein:

Figure 1 is a perspective view of a drill having the safety attachmentconnected therewith.

Fig. 2 is a view partially in section and partially in elevation showingthe attachment connected with the drill carriage and held in theinoperative position by the supporting chain for the drill. v

This safety attachment is shown in use as applied to a large drill whichis indicated in general by the numeral 10 and is of a conventionalconstruction. This drill is further provided with a carriage 11 which isslidably mounted upon a track 12 and provided with the usual feedingmechanism 13 for engaging the teeth of the rack 16 and moving thecarriage vertically upon the track. A supporting'chain 1a is connectedwith the carriage by means of the usual bolt 15 and this chain will becarried over suitable guides and having its second end connected with acounterbalancing weight so that the weight of the drill and carriagewill be counterbalanced and thus the drill permitted to be easily movedvertically upon the track. The structure so far described is of aconventional construction and therefore has not been described in detailand it is to be understood that it is not desired to confine theinvention to the specific drill shown as it can be used in connectionwith any device which is slidably mounted upon a track including a toothbar or rack 16 for engagement by actuating mechanism for moving thetrack.

This attachment is in the form of a locking pawl 17 which is pivotallymounted between the bearing brackets 18 by means of the pin 19 so thatit will be movable into and out of engagement with the teeth of the rack16 It should be noted that the free end of the pawl is formed into anose 17 which will fit between the teeth of the rack when the pawl isswung into engagement with the rack. These bearing brackets 18 are heldin lace by suitable securing screws and it w1ll thus be seen that theycan be easily applied to the carriage 11. The pawl 17 is provided with ahandle extension 20 which extends upwardly and terminates in a head 21for engaging the supporting chain let and thus holding the pawl 17 inthe,

inoperative position shown. An actuating lever 22 extends from theupperend portion of the pawl at substantially right angles to the handleextension 20 and hasits free end portion provided with an opening 23through which the upper end of the spring 24 may be passed to connectthe spring with the actuating lever. This spring 24 has its lower endconnected with the eye bolt 25 screwed into a threaded opening of thecarriage and it will be readily seen that when the chain breaks, thecontraction of the spring will cause the pawl to swing upon its pivot 19and into engage ment with the rack 16 with the nose 17 fitting betweenthe teeth of the rack. The carriage will thus be locked againstdowndevice longitudinally of the ward sliding movement and danger of anoperator being injured by the drill falling upon him or danger of adrill or work being broken by the fallen drill prevented.

' When a new chain is put in place the drill will be moved upwardly byits shifting mechanism 13 and the pawl will thus be relieved frompressure and can be easily swung to an inoperative position with thehead Qlpositioned to engage the chain. The chain will retain it in theinoperative position until the chainagain breaks.

What is claimed is:

The combination with a machine of the character described including atrack, atoothed rack extending longitudinally of the I track and acarriage slidably mounted upon the track and including actuatingmechanism for operatively engaging the teeth of the rack, of asuspending cable for the carriage extending in spaced relation to thetrack, a pawl pivotally mounted and having its free end portion formedinto a nose for fitting between the teeth of the rack when in anoperative position to hold the carriage against downward slidingmovement, an abutment arm extending from the pawl and extending forengagement with the cable to hold the pawl against pivotal movement andretain the pawl in an inoperative position while the arm is inengagement with the cable, an actuating lever extending from the pawl,and means connected with the actuating lever for imparting movement tothe lever and swinging the pawl into engagement with the rack when theabutment arm is out of engagement with the cable.

In testimony whereof I have hereunto set my hand.

HENRY V. JOHNSON.

